The present invention relates to a gearing arrangement for a vertical mill.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Vertical mills are used in the building materials industry for the purpose of breaking up limestone, clinker, slag, chalk, gypsum and coal, and in the processing of coal.
FIG. 1 shows a side and partial sectional view of a conventional vertical mill 20 having a mill housing 22 which forms a milling space 29 with a rotatable milling plate 23, onto which material to be milled are fed from above. Milling rollers 24 which roll on the milling plate 23 comminute the material on the milling plate 23. For feeding the material and airflows into the milling space 29, the mill housing 22 has openings in its upper part, which can be closed off by covers 28, 30. The mill housing 22 is carried by a support structure 26, which in turn is supported on a mill foundation 18, which creates space beneath the milling space 29 for a drive device 10 for operating the milling plate 23. The drive device 10 is also supported by the mill foundation 18 and includes a drive motor 12, a gearing arrangement 1, and a coupling 14, which connects an output shaft from the drive motor 12 to an input shaft on the gearing arrangement 1. The coupling 14 can be a hydrodynamic coupling, a high-flexibility coupling, or the like.
The gearing arrangement 1 is a beveled gear planetary gearing, which has on its input side a beveled gear stage which turns the rotation axis by 90 degrees, and at least one planetary gearing stage downstream from the beveled gear stage on the output side. Beveled gear planetary gearings of this type are commercially available from Siemens AG under the designation KMP and KMPS. An output flange 16 of the gearing arrangement 1 transmits the rotation of the planetary gearing stage on the output side to the milling plate 23. The output flange 16 is connected to the milling plate 23 using a sub-construction 17, which is in the form of a truncated cone which tapers in the downward direction.
U.S. Pat. No. 7,926,754 describes an actively redundant drive system for roller mills. Continuous availability of at least two drives is assured by the arrangement of more than two drives, wherein the at least two drives supply the necessary milling power for the roller mill. Each of the drives has a pinion gear which meshes with a crown gear arranged underneath the milling plate. Each drive module incorporates an electric motor, a coupling and a beveled/spur gear drive, arranged on a base frame as the transport unit. If one drive fails, this drive can be withdrawn on a carriage from its toothed engagement, without interrupting the milling process.
To compensate angular deviations between the axes of the pinion gears and the crown gear as a result of operating conditions, the pinion gears must be mounted so that they can move in a tilting direction. Sealing the oil lubrication of the toothed engagement between the pinion gear and the crown gear is complex and thus possible only at considerable cost.
EP 2025409 A1 describes a mill drive for roller mills with a beveled gear stage for feeding in the power and at least one planetary gearing stage for the power output on the milling bowl side. Instead of a single large drive, the beveled gear stage has several separate drives and corresponding beveled pinion gears, which are arranged to engage jointly with the beveled gear. A beveled gear stage with several separate drives, such as is described in EP 2025409 A1, requires adjustment in order to achieve a satisfactory bearing pattern between the flanks of the teeth on the beveled gear and on the beveled pinion gears which mesh with them. This adjustment is generally, effected by an axial displacement of the shafts involved. Adjusting the beveled gear shaft for all beveled pinion gears which engage with it requires a compromise, which does not result in optimal bearing patterns for all the beveled pinion gears, and hence results in restrictions in the performance of the beveled gear stage. Consequently, for the purpose of balancing them out, the components must be appropriately oversized. This is expensive.
It would therefore be desirable and advantageous to provide an improved transmission for a vertical mill to obviate prior art shortcomings.